Enzymatic Fuel Cells Solely Supplied with Unpurified Cellobiose Dehydrogenase and Laccase in Microorganism’s Culture Supernatants

Cellobiose dehydrogenase in biofuel cells

Enzymatic biofuel cells utilize oxidoreductases as highly specific and highly active electrocatalysts to convert a fuel and an oxidant even in complex biological matrices like hydrolysates or physiological fluids into electric energy. The hemoflavoenzyme cellobiose dehydrogenase is investigated as a versatile bioelectrocatalyst for the anode reaction of biofuel cells, because it is robust, converts a range of different carbohydrates, and can transfer electrons to the anode by direct electron transfer or via redox mediators. The versatility of cellobiose dehydrogenase has led to the development of various electrode modifications to create biofuel cells and biosupercapacitors that are capable to power small electronic devices like biosensors and connect them wireless to a receiver.

Cellobiose dehydrogenase: Bioelectrochemical insights and applications

Cellobiose dehydrogenase (CDH) is a flavocytochrome with a history of bioelectrochemical research dating back to 1992. During the years, it has been shown to be capable of mediated electron transfer (MET) and direct electron transfer (DET) to a variety of electrodes. This versatility of CDH originates from the separation of the catalytic flavodehydrogenase domain and the electron transferring cytochrome domain. This uncoupling of the catalytic reaction from the electron transfer process allows the application of CDH on many different electrode materials and surfaces, where it shows robust DET. Recent X-ray diffraction and small angle scattering studies provided insights into the structure of CDH and its domain mobility, which can change between a closed-state and an open-state conformation. This structural information verifies the electron transfer mechanism of CDH that was initially established by bioelectrochemical methods. A combination of DET and MET experiments has been used to investigate the catalytic mechanism and the electron transfer process of CDH and to deduce a protein structure comprising of mobile domains. Even more, electrochemical methods have been used to study the redox potentials of the FAD and the haem b cofactors of CDH or the electron transfer rates. These electrochemical experiments, their results and the application of the characterised CDHs in biosensors, biofuel cells and biosupercapacitors are combined with biochemical and structural data to provide a thorough overview on CDH as versatile bioelectrocatalyst.